We have deliberately used the word "definition" in the plural because there is no single standard definition of high speed rail (nor even a standard usage of the term: sometimes it is called "high speed" and sometimes "very high speed"). The definitions vary according to the criteria used since high speed rail corresponds to a complex reality. We on the UIC High Speed Taskforce wanted to reflect this diversity by considering high speed from all the standpoints: infrastructure, rolling stock and operating.
First of all there is the European Union definition, given in Directive 96/48; this is a fairly broad definition which encompasses a large number of systems under the banner of high speed.
But it is also necessary to take into account those railways which are making laudable efforts to provide high speed despite a basis of old infrastructure and technology which is far removed from that employed by the railways of western Europe.
At all events, high speed is a combination of all the elements which constitute the "system": infrastructure (new lines designed for speeds above 250 km/h and upgraded lines for speeds up to 200 or even 220 km/h, some worked with tilting trains, some not), rolling stock and operating conditions. In view of the fact that many high speed trains are also compatible with the conventional network, the term "high speed traffic" is also frequently understood to signify the movements of this type of train on conventional lines but at speeds lower than those permitted on the new high speed infrastructure. Consequently, on some lines which are claimed to be high speed lines it is very difficult to specify a threshold when, in certain very densely populated regions, the speed is restricted to 110 km/h in order to avoid noise nuisance, or where, as in special tunnel sections or on long bridges, the speed is limited to 160 or 180 km/h for obvious reasons associated with capacity or safety. Finally, in many countries where the performance of the conventional railway is not very high, the introduction of some trains capable of operating at 160 km/h and offering a significant level of quality - often as a first step towards a future genuinely high speed service - may already be considered as high speed.
The highspeed definition of the European Union :
DIRECTIVE 96/48/EC APPENDIX 1
a) The infrastructure of the trans-European High Speed system shall be that on the trans- European transport network identified in Article 129C of the Treaty:
- those built specially for High Speed travel,
- those specially upgraded for High Speed travel. They may include connecting lines, in particular junctions of new lines upgraded for High Speed with town centre stations located on them, on which speeds must take account of local conditions.
b) High Speed lines shall comprise:
- Specially built High Speed lines equipped for speeds generally equal to or greater than 250 km/h,
- Specially upgraded High Speed lines equipped for speeds of the order of 200 km/h,
- Specially upgraded High Speed lines which have special features as a result of topographical, relief or town-planning constraints, on which the speed must be adapted to each case.
2. Rolling stock
The High Speed advanced-technology trains shall be designed in such a way as to guarantee safe, uninterrupted travel:
- at a speed of at least 250 km/h on lines specially built for High Speed, while enabling speeds of over 300 km/h to be reached in appropriate circumstances,
- at a speed of the order of 200 km/h on existing lines which have been or are specially upgraded,
- at the highest possible speed on other lines.
3. Compatibility of infrastructure and rolling stock
High Speed train services presuppose excellent compatibility between the characteristics of the infrastructure and those of the rolling stock. Performance levels, safety, quality of service and cost depend upon that compatibility.